| 摘要 |
PURPOSE:To make a dielectric constant in a porous layer section smaller than more dense ceramics, and to shorten the propagation delay time of a signal transmitted to internal conductor paths by separately forming conductor paths to the porous layer section and the surface of a dense layer and electrically connecting the porous layer and the dense layer through through-holes and via holes. CONSTITUTION:A plurality of porous layers 4 and dense layers 6 formed on both upper and lower sides at every one layer are laminated mutually in a low-dielectric- constant board 2, and the porous layers 4 and the dense layers 6 are both composed of ceramics. Conductor paths 8a are shaped among the layers and insides of the porous layers 4 and conductor paths 8b onto the surfaces of the dense layers 6 respectively, and both the conductor path 8a and the conductor paths 8b are connected electrically through through-holes 10. Since the porous layers 4 include a large number of pores having a low dielectric constant, the dielectric constant of the porous layers 4 is made smaller than dense ceramics, and a dielectric constant as the whole board is reduced. Accordingly, the propagation delay time of a signal transmitted to the internal and external conductor paths 8a, 8b, particularly the internal conductor paths 8a can be shortened. |
